Explosion-proof lighting unit



1942- M. J. GIRIFFIN 2,304,085

EXPLOSION. PROOF LIGHTING UNIT Filed Feb; 19, 1940- w 2 Sheets-Sheet 1 Meinam J Grgffin 8, "M. J. GRIFFIN EXPLOSION PROOF LIGHTING UNIT Filed Feb. 19, 1940 2 Sheets-Sheet 2 mightoccun.-

.Patented'Dec. 1942- UNITED STATES PATENT'I-OFFICE 2,304,085 y I a Metram r. Grlflin, New York, N. Y.

Application February 19, 1940, Serial No. 319,801

' 1s Claims. (01. 240-113) The present invention relates to explosionproot lighting units adapted to be used in mines,

, industrial plants and otherplaces where an explosive atmosphere is apt to be present.

. It is a principal object of the invention to provide an electric lighting unit, wherein all parts which'might ignite an explosive atmosphere are isolated from that atmosphere in an enveloping body or high pressure, non-combustible gas.

It isa iurtherobject oi the invention to prowithin the isolated area, responsive to a drop in pressure to extinguish the lamp. Hence, the

light bulb and associated parts will cool down below theignition point of the explosive atmos- .phere before the latter can come into contact invention must be removed from its supporting,

structure before it can be relighted, thereby substantially "completely obviating the danger of inflating the unit with an explosive mixture of gas and air.

in the past, lighting units have been con- I structed wherein internal pressures above atmosphere have-been maintained, in an attempt to prevent theentrance of explosive gases into the units, and pressure responsive switches to deenergizethe lamp circuit upon a drop in pressure havebeen provided. .'However, in all such devices, the circuit controlling switches were adapted to be shifted to circuit-closing position simply by re-inflating the units. Hence, a careless or ignorant person, in an attempt to re-light the unit, might inflate the same with air containing explosive gases, with the result that an explosion As stated above, the-principal object of the present invention is to construct an explosionproof lighting unit-oi the high pressure type which cannot be made operative after a, pressure drop by merely raising. the pressure within the casing tion will be apparent to one skilled in the art from a-consideration of the illustrative embodiments of the invention shown in the accompanying drawings and described below In the drawings:

- Figure 1 is a vertical sectional view of a light= t parts being shown in elevation. i

. vide' an automatic circuit controlling. device ing unit in accordance with the invention, certain Figure 2 is a similar view 0! a modification, and Figure 3 is a horizontal sectional view, taken 'onlineS-i oiFigure2.

The modification oi the invention shown in Figure 1 comprises generally an illuminating device such as a lamp I, a reflector casing 2 with a light permeable portion 8. The casing 2 is attached to a housing 4 carried by an outlet flxture I mounted on a power conduit 6.

In the housing 4, thereis positioned a snapaction toggle switch I having an operating arm 8 adapted to be moved by contact with an insulated block 9 carried bya'thin flexible, metallic diaphragm ll. This diaphragm II is normally forced downwardly by a coil compression spring ll mounted between the top side of the dia 'phragm and the top of the housing 4. Thecasing Llandthehousinglbelowthe,

diaphragm l0 constitute a single high pressure chamber. Gaskets it between the upper and lower parts of the housing 4 make an air-tight joint between the diaphragm II and the housing 4. Gaskets 20, II at the point or Junction between the casing 2 and the housing 4 prevent any leaks therebetween. A hollow boss 22 pro- Jecting from a wall of the casing carries a oneway valve such as a standard pneumatic tire valve, which will allow a pressure to .be built up within thelower hall! of the housing 4 and the 'casing 2, 3.

Attached to the end of the switch arm a is a weighted ball 2: having adjustable screw :4

, trolled. The weighted member 23' is a very important feature of my invention. Its mass is so proportioned to the resistance or the switch I that it will be insufficient to move the switch arm 8 from the circuiteclosing position shown in Figure l by the force of gravity, but its mass is suiiicient to move the arm 8 upwardly by a' sudden downward movement of the whole unit.

.0! course, the unit cannot'be moved downwardly 'until the housing .4 is separated from the flxturel.

, Mounted'in the insulated block 0, carried by the diaphragm II, are two air-tight conducting portions i: which are connected to power-lines H-H and l5-l5. Wire's 'liareattached to ,Thebperatlonoi the device s'hown in'Pigure} and broadly described above is as A high pressure fluid such as air or anon-in flammable gas is forced into the housing] through the valve. until any desired pressure is -is, the pressure within the balance the force of the spring ll tending to 'fixture 5. A set screw built up within the housing 4 and the casing 2, 3. When this pressure is stablished, the diaphragm It will be in the position shown in Figure 1, that housing 4 will just move the diaphragm l downwardly. It the pressure for any reason should fall within the housing and easing, the spring II will force the diaphragm i0 downwardhr to contact theadjustable screw 24 in the weighted ball 23 attached to the end of the switch arm. 8. Continued downward movement of the diaphragm l8 will move the switch 'arm 8 past the dead center position of the toggle switch I and the switch arm 8 will be snapped to its lowermost position and the circuit to the lamp I will be opened. If some unauthorized person should attempt to relight the lamp by applying a source of air pressure to the valve 22, the diaphragm ill will move upwardly butthe switch arm 8 will stay in its lowermost position and the switch 1 will remain open. In order to put eration, itis necessary to separate the housing 4 from the fixture 5, build up the pressure within the housing 4 and then shake the whole unit so that the mass of the weighted member 23will move the switch arm,8 upwardly. When the housing 4 is again'attached to the fixture 5 and the socket l1 and plug l8 are properly positioned, the lamp will be-readyfor operation.

- By thus making it necessary. to completely remove the housing 4 from the fixture 5, the chance of someunauthorized or ignorant person re-inflating the housing is very slight. Anyone who will go to the trouble of removing the housing from its fixture will normally, ascertain main points of difference are that, in this construction, a Sylphon bellows is used, instead of a flexible diaphragm, and the switch actuating arm is of slightly different construction. As in Figure l, the lamp I is enclosedin a casing 2 having alightpermeable portion 3 all connected to the housing 4. Mounted in the housing 4 is a switch 1 which may be a rotary snap switch instead of the toggle switch shown in Figure 1. A

Sylpho'n bellows 381s disposed within the housing 4, with its interior in communication with the outside atmosphere through a passage 48. Attached to the top of the bellows 38 is a saddle 4| having downwardly and outwardly projecting lugs 42, which are disposed beneath the arms of 'a forked lever 43 pivoted at 44 on the housing 4 as shown in Figure 3. The other end of the the lamp back into opg or other fluid into the housing t and the casing 2, 3. The valve structure may include an ordinarypneumatic tireyalve inside and valve cap;

'where the leak is and repair it? orthwith'.-- In or- Y der to absolutely preventany unauthorizedperson fromresetting the switch, a lock may be pro-' videdbetween the housing 4 and the fixture 5 so that the housing cannot possibly be removed. No lock is shown in the accompanying drawings as any conventional type may be used.

In addition to. the broadfeatures' described above, the invention also includes certain teatures of construction which make the unit par ticularly inexpensive to manufacture and simple to assemble. The housing 4 is divided into upper I and lower portions 4a and 4b respectively, which facilitates ready access to the switch members.

Mounted on' the portion 4b is an upwardly extending flange 25 upon which any standard toggle switch may be mounted by means of nuts 28. The housing 4b has a downwardly extending throat 21 externally screw-threaded to. receive a nut 28 adapted to hold the casing 2 in air-tight relationship to the housingl. Screwed below the nut 28 is another nut 28 which holds the bracket 38, which in turn supports the lamp base l8.

Fortion 4a of the housing 4 has an upwardly and outwardly extending lip 3| which is extemally screw-threaded to hold a ring nut 32 adapted to engage a laterally extending flange 33 on the 34 on the ring nut 32 engages a portion 35 on the fixture 5 and holds the ring nut against movement.

An inwardly extending flange 38 at the top of section 4a of the housing has an annular ridge 31 which acts as a seat for the spring H. The other end of the spring II is seated on an upwardly projecting lug 38 on the insulating block 8 carried by the diaphragm l0.

. In the modification in the Figure 2, many of the features of construction are similar to those shown in Figure 1. The

invention shown in lever 43. is connected to the switch arm 45 by means of an adjustable link 46. The top of the housing 4 is sealed by means of the plug I8 and the gaskets 41.

A one-way valve 22 is provided for pumping air Gaskets I8, 28', 21' similar to those shown in Figure 1, make the housing 4 andits connection with thecasing 2 air-tight. The Joint between the reflector casing 2 and the glass plate 8 may be sealed by a gasket 48, a V gasket 49 and a com- Q position shown in Figure 2. If a leak occurs, thepressure difierentialbetween-the inside and outside of the bellows is decreased and the bellows will rise, thereby swinging the lever 43 upwardly around the pivot 44. The movement of the lever 43 will move the switch arm 45 by means of the link 48 to open the switch I. An increase in pressure will contract and depress the bellows, but since there is no positive connection between the outwardly extending lugs 42 on the saddle 4| and the lever 48, therewill be no force tend ing to move the arm 48 downwardly and the switch will remain in the open position. Switch actuating arm 43, like switch actuating arm 8 and weighted ball 23 described in Figure 1, is comparatively heavy.- Its mass is so adjusted that the force of gravity tending to rotate the lever 48 downwardly around the pivot 44 will be insufllcient to cause a movement due to the resistanee of the snap switch 1. However, its'mass is sufllcient to cause a downward motion when the casing is moved suddenly upwardly, or moved downwardly and stopped suddenly. Thus it will be apparent that the whole unit shown in this modification will have to be removed from the fixture 5 before the switch can be reset after the pressure has been built up within the housing and easing.

In the normal use of my invention, these light ing units will be operating in a highly explosive atmosphere and the danger of repressuring these units when there is any explosive gas inside of the unit will necessitate their careful supervision. By making the whole unit removable, whenever the pressure drops therein, the unit may be detached from the fixture 5 and taken out of I the gas zone to be inspected.

paired. The pressure will then be built up within the unit and the switch may be reset by merely shaking the unit. The whole unit in its reset condition may then be moved back to the gas zone and reattached to the fixture. By providing the straight line type of plug at the top of the unit, it is a simple matter to attach this unit to the electrical outlet.

There are many other features of construction of the device shown'in Figure 2 which are similar to corresponding parts shown in Figure l The housing 4 is divided into upper and lower portions la and 41), respectively, while portion lb has a downwardly extending, internally threaded throat 21 upon which are screwed the nuts 28, 2'9 and the bracket 30 supporting the lamp socket IS.

The top construction of portion 4a likewise has a laterally extending lip 3| and a ring nut 32 adapted to engage a laterally extending flange 33 of the fixture 5. The plug l8 and socket I! are of the usual type and need not be discussed in detail.

The diflerent wires shown injFigure 2 correspond to like wires in Figure i.

From the above description, it will be readily apparent that I have invented an extremely simple lighting unit which may not be relighted after failure by an ignorant or unauthorized employee, thus completely obviating the danger of an explosion caused by turning on. the switch while any explosive gases are inside of the casing. A further advantage is that the whole unit may be readily transported to any safeplace for repairs and reset only by some person who has carefully inspected the lamp to correct-any failures. This lighting unit is extremely simple to construct and repair and may upon an increase in the pressure in the casln: above said predetermined minimum.

2. An explosion-proof lighting unit of the type described in claim 1 whereinsaid switch is of the snap type and positively maintains itself at either of the two positions to which it is moved by the switch operating member. I

3. An explosion-proof lighting unit of the type I 7 described in claim 1 wherein said switch operating member and said pressure responsive element are so arranged as to provide a lost motion, oneway connection therebetween.

4. An explosion-proof lightingunit of the type described in claim 1 wherein said pressure responsive means comprises a bellows, the inside of which is in communication with atmosphere outside of said casing.

. 5. An explosion-proof lighting unit of the type described in claim 1 wherein said pressure responsive means comprises a movable diaphragm one side of which is in communication with atmosphere outside of said casing.

- 6. An explosion-proof lighting unit comprising an illuminating device, an air-tight casing surrounding said illuminating device, means for maintaining a super-atmospheric pressure within said casing, a switch in circuit with said 'illuminating device, means movable in response to variations in the pressure diflerentialbetween the inside and outside of said casing, a switch operating member, said pressure responsive means being operable to move in one direction Y upon decrease in said pressure differential and to move in another direction upon increase in said pressure differential, said switch operating member when in switch closing position being in the pathof movement of the pressure responbe readily applied to lighting systems now in for normally maintaining a superatmospheric pressure therein, a switch in circuit with said illuminating device, a switch operating member movable in opposite directions between a switch opening position and a switch closing position,

and means responsive to the pressure in the casing including an element movable in opposite directions in response to increases and decreases in said-pressura'said switch operating member when in switch'closing position being disposed directly in the path oi movement followed by said element when the pressure in the casing falls below a predetermined minimum, said member being movable from switch closing to switch opening position by'contact with said element during such movement. to open the switch and said circuit, said member when in switch opening position being out of the path of movement of said pressure responsive element whereby said element is free to move in the opposite direction independently of said switch operating member sive means in the first mentioned direction, whereby a decrease in the pressure differential moves the member and opens the switch, the

switch operating member when in switch opening position being out of the path of movement of the pressure responsive means in the second mentioned direction, whereby an increase in the pressure differential moves only the pressure responsive means and leaves the switch unaffected.

'1. An explosion-proof lighting unit comprising an illuminating device, anair-tight casing surrounding said illuminating device,- means for maintaining super-atmospheric pressure within said casing, a switch in said casing and in circuit with said illuminating device, pressure responsive means,- a switch operating member positioned in the path of movement of said pressure responsive means to be moved thereby to actuate said switch to open said circuit whenever the pressure differential between the pressure inside said casing and outside said casing falls below a predetermined minimum, said pressure responsive means being movable independently of said member upon an increase in said pressure differential,

thereby leaving the switch in the circuit opening position, said switch operating member being pivotally mounted for movement to switch clos-iing position and having sufllcient mass to be moved to that position by shaking said unit when the pressure differential is above said predetermined mlnimum.

8. An explosion-proof lighting unit comprising an illuminating device, an air-tight casing surrounding said illuminatingdevice, means formaintaining a super-atmospheric pressure within said casing, a switch having a predetermined mechanical resistance to movement in said casing and in circuit with said illuminating device, pressure responsive means, a switch operating memher in the path of movement or said pressure responsive means to actuate said switch to open said circuit whenever the :pressure diflerential between the pressure inside said casing and outside said casing falls below a predetermined minimum, said member having a mass insufficient to cause movement of saidconnecting means by I gravity against the mechanical resistance to movement oi said switch but sufllcient to cause movement of said member to close the switch by u a sudden movement oi said casing.

9. An explosion-proof lighting unit comprising an insulating portion in said last named portion having upwardly extending. electrical contact prongs, all'oi. said portions being in communication with each other and forming, an air-tight c i 14. An explosion-proof lighting unitcomprising an illuminating device, an air-tight casing surrounding said illuminating device, means for maintaining a super-atmospheric pressure within said-casing, a switch in circuit with said illuminating device, a movable diaphragm responsive to the pressure differential between the inan illuminating device, an air-tight casing surj .-rounding said illuminating device, means for maintaining a super-atmospheric pressure withinsaid casing, a switch in said casing in circuit with saidv illuminating device, a pressure responsive bellows having one side in comunication with the atmosphere outside of said casing, a switch operating member, an'element on said bellows positioned to engage said member to move the same and open said switch upon movement or said bellows in response to decrease in pressure differential between the inside and outside of said casing, said member when in switch opening pocasing, a saddle on said bellows, a iturcated arm. having connection at one end with saidswitch.

said bifurcated portion being positioned to be engaged by said saddle but not connectedthereto.

'11. An explosion-proof lighting unit comprising an illuminating device, an air-tight casing surrounding said illuminating device, means for maintaining a super-atmospheric pressure within said casing, a snap switch mounted in said casing having-an operating arm connected thereto, a vertically positioned bellows having communication with the outsideatmosphere at its lower end, said arm having a biiurcated portion positioned to extend partially around said bellows, a saddle on saidbellows having horizontally positioned lugs adapted to engage the underside of said bifurcated arms whereby upward movement of said bellows and said saddle due to decrease in pressure within said casing will move said hiiurcatedarm upwardly to turn oil said switch, but the downward movement or said bellows,

when said switch is in the oil position, will be inoperative to turn said switch on.

,12. An explosion-proof lighting unit of the type said bellows is in its depressed position and said casing is moved suddenly upwardly but has insuflicient mass to movedownwardly against the resistance or the switch under the influence oi gravity.

13. An explosion-proof lighting unit of the type described in claim 11 wherein said casing comprises an illuminating device enclosing portion, a switch and bellows enclosing portion, and

side and outside of said casing and a switch arm on said switch positioned to be contacted by said diaphragm when said diaphragm moves in one direction in response to a decrease in pressure diflerential, said dia hragm being free to move in the opposite direction independently of said am in response to an increase in pressure diiierential.

is. An explosion-proof lighting unit 01' the type described in claim 14 wherein a spring is I described in claim ll wherein said operating arm has sufllcientmass to close said switch. when mounted on the.low pressure sideoi said diaphragm Y 16. An explosion-proof lighting unit -01 the typedescribed in claim 14 wherein said arm has on its end remote from said switch aweight or suflicient mass to cause movement oi said am when said casing is moved suddenly, but of in suflicient mass to move said arm by gravity against the resistance of the switch.

, 17. An explosion-proof lighting unit comprising an illuminating device, an air-tight casing surrounding saidilluminating device, means for maintaining a super-atmospheric pressure within said casing, a switch in circuit with said illuminating device, a movable diaphragm respon-.

sive to the pressure diiierential between the in side and outside of said casing and a switch arm ,on said switch positioned to be contacted by said diaphragm when said diaphragm moves in one direction in response to a decrease in'pressure differential, said diaphragm being free to move in the opposite direction independently of said arm in response to an increase'in pressure difierential, and an adjustable contact on said arm to'vary the pressure diflerential at which said diaphragm will contact said am and move said arm to open said switch.

18. 4n explosion-proof lighting unit comprising an illuminating device, an air-tight casing surrounding said illuminating device, an electrical power outlet, a two-part housing, a first part oi. said housing being removably attached to said outlet, a second part of said housing being removably attached to said casing, a ilexible diaphragm mounted between the junction of the two parts of said housing, the second part of said housing, said diaphragm and said casing forming an air-tight compartment, means for maintaining a super-atmospheric pressure in said compartment, a switch mounted in said second part 01' said housing in position to be moved to circuit opening position by movement of said diaphragm in response to a decrease in' the pressure in said air-tight compartment, an electric plug mounted in-said outlet and a cooperating electric plug mounted in said first part of said housing and power leads extending from said second mentioned plug through said diaphragm to said switch and said illuminating device.

names; J. GRIFFIN. 

